I received a reply from a rep at Holan. A group buy of from 3 to 5 units would get a 10% discount, more than 5 units = 15% discount. However, 20kg is the most weight that a shipped parcel can be. That equates to 3 sets of crash bars (one set weighs 5,5kg, the same with pannier rack, the headlight protector is 0,3kg). The cost of shipping a 20kg parcel is 130 Euro. Once they arrived here and were redistributed to those who are interested in participating in a group buy, there'd be an additional domestic shipping charge according to where each unit was headed. Maybe Adventurers Workshop or some other vendor can work a better arrangement than I can.